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Old 12-28-2014, 09:13 AM
 
Location: Vallejo
14,060 posts, read 16,066,811 times
Reputation: 12635

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Quote:
Originally Posted by nybbler View Post
The Fourth Power law really only applies to heavy vehicles (tens of thousands of pounds per axle). It's not valid for lighter weights; basically there are modes of pavement damage which simply do not occur for anything as light as a Suburban. If a road is built to carry trucks, road wear from cars (whether Suburbans or Priuses) is negligible. I'm unaware of studies to determine relative road damage between light vehicles on less-strongly-built roads.
It's napkin math from the 1950s. Road wear is always negligible for anything, including trucks. Fourth power law is about aggregates damage. It turns out when you take an aggregate of thousands of vehicles per day for years the negligible damage caused by any one of those vehicles actually isn't negligible.

GAO put the comparable damage between a typical 5-axle truck loaded to the federal limit (80,000 pounds) at about 9,600 times the damage of a passenger car. That's common knowledge since AASHTO has run several studies on just that.
http://archive.gao.gov/f0302/109884.pdf

How does that compare with a Fourth Power Law estimate?
front axle (12,000/2000)^4 =1,296
trailer axles (17,200/200-)^4 =5,220. And there's four of them so 20,880.
20,880+1,296 = 22,176.
And then a car has two axles, each carrying 2,000 pounds. 22,176/2=11,088.

So how accurate is the Fourth Power Law at approximating the difference between an 80,000 pound truck and a 4,000 pound passenger vehicle? Pretty close. It overestimates by about 15-16%.

Is a passenger vehicle doing roughly a hundredth of a percent of the damage of a truck negligible? You could certainly say that. I wouldn't argue with it. And yes, those numbers are for federal-aid highways. Roads built for lighter use would, I assume we can agree here, not hold up as well to higher axle weights hence the Suburban would be even more subsidized. Regardless, with the Fourth Power Law being accurate enough for this discussion between a 80,000 pound truck and a 4,000 pound car, it's going to be much more accurate between a 5,600 pound Suburban and 3,000 pound compact.

I didn't say the Fourth Power Law should be used. If instituting an axle weight mileage fee, it would be far more appropriate to use the best available data which is not the Fourth Power Law.
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Old 12-28-2014, 10:03 AM
 
2,824 posts, read 3,347,681 times
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Quote:
Originally Posted by Komeht View Post
People don't realize what a tectonic shift this will be for cities. The FHWTF is broke. To fix it would mean to raise taxes beyond what is politically feasible (a 5 or 10 cent bump won't come close). Almost all the DOTs are operating deep in the red. There is no money for new construction and the aging infrastructure gets more expensive each day to maintain. A few trends to look to:

1. No new urban freeways. Those are history. The cost to barrel through a urban core and ROW acquisition far exceeds what is fiscally possible. Same goes true for roadway expansions. To do any project, the DOTs will have to confine themselves to existing ROW (if at all).
Dream on.

Quote:
Originally Posted by Komeht View Post
2. No new freeways. Almost all new roadways will be tolled. That's the only way to finance projects going forward.
Dreaming again. So much for your cut & cap I-35 dream if that were the case - because that's effectively a completely new roadway.

Quote:
Originally Posted by Komeht View Post
3. The financial analysis on toll roads will ultimately be a lot more rigorous. These will involve PPP financings - there will be successes and failures and a lot of analysis spent on determining what makes a road a success or a failure. Over time this will weed out more bad projects in a way that pure public financing could never accomplish because it was never subject to the scrutiny of the market.
....shouldn't your cut & cap I-35 plan be subject to the scrutiny of the market or do you rely upon pure public finance to avoid rational economic scrutiny?

Quote:
Originally Posted by Komeht View Post
4. Much of the aging infrastructure will be abandoned rather than repaired and replaced. It's already starting, but this process will accelerate as the balance of power to determine these things shifts away from the DOTs. Success will breed success and this process will accelerate though the 21st Century (The Century of the City)
The century of the city passed a while back. Every century is a century of population growth generally. No one questions whether there will be changes in infrastructure - just like there will be changes in cities some of which may grow others which will shrink at any point in time. Think Detroit.

Quote:
Originally Posted by Komeht View Post
5. DOTs will find themselves shifting away from being rubber tire highway departments and return to being transportation departments - the balance will shift away from pure rubber tire single occupancy vehicle solutions and towards transit and other alternative modes for transportation.
see below

Quote:
Originally Posted by Komeht View Post
6. DOTs will return lesser roads to municipalities. These are typically the state highways that turn into stroads through urbanized areas. In an effort to maintain money, control will be turned to Municipalities who will then have a lot more control over the character and nature of the stroads - look for road diets, muli-modal implementations and more creative uses of the ROW.

7. Finally - there will be a return to the original mission of the DOTs - connecting productive places together, not going through them - that will be returned to the Cities.
Hmmm. So the cities should bear the financial burden of all roads through the city - which places the city in a position to harm not only intrastate commerce but also interstate commerce. I don't think many would trust the city of Austin to be responsible with respect to maintaining roads. The city council (under former representation schemes) generally took an anti-construction stance. That will change given the change to single member district as opposed to the downtown crowd.

Given this new mission and the financial state of DOTs, perhaps they should not contribute a dime to "in city" transportation projects such as the $97 million streetcar project in El Paso (another boondoggle)? Yup the DOT could improve its financial condition by not providing monies for any in-city transportation projects.

State trumps city and the budget for DOTs is mostly at the whim of a legislature - so your predictions here are more of an activist urbanist wishlist than an accurate prediction of things to come. Guess what? People (not corporations) vote. The contingent opposing roads is smaller than the contingent that wants or needs them. Moreover, your downtown area is heavily populated with businesses - which can contribute money but can't vote. Those businesses want the very roads you seek to eliminate - for clients as well as for employees (none of few of whom live downtown).
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Old 01-02-2015, 11:48 AM
 
Location: East of Seattle since 1992, originally from SF Bay Area
29,762 posts, read 54,390,602 times
Reputation: 31056
Quote:
Originally Posted by IC_deLight View Post
Dream on.


State trumps city and the budget for DOTs is mostly at the whim of a legislature - so your predictions here are more of an activist urbanist wishlist than an accurate prediction of things to come. Guess what? People (not corporations) vote. The contingent opposing roads is smaller than the contingent that wants or needs them. Moreover, your downtown area is heavily populated with businesses - which can contribute money but can't vote. Those businesses want the very roads you seek to eliminate - for clients as well as for employees (none of few of whom live downtown).
Here in Seattle the current major 3.1 billion dollar tunnel project (a year behind now) is totally within the City, but being done under the control of the state DOT, with mostly funds from the state but also some federal and local sources.

The state is also, at the same time, building a new 4.3 billion dollar bridge.


WSDOT - SR 520 Bridge Replacement and HOV Program
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Old 01-02-2015, 11:47 PM
 
2,824 posts, read 3,347,681 times
Reputation: 3030
Quote:
Originally Posted by Hemlock140 View Post
Here in Seattle the current major 3.1 billion dollar tunnel project (a year behind now) is totally within the City, but being done under the control of the state DOT, with mostly funds from the state but also some federal and local sources.

The state is also, at the same time, building a new 4.3 billion dollar bridge.


WSDOT - SR 520 Bridge Replacement and HOV Program
Not sure how that is supposed to relate to my comment which was quoted. However, it appears that it is an example of road building funded and controlled by the state (not the city) which is consistent with my quoted statement. The fact that a road is located within or passes through a city does not necessarily mean that the city will have any say over the road. A city's level of control and obligation for maintenance typically depends on where the road falls in the hierarchy of roads. Interstates, state highways, farm-to-market, ranch-to-market, ranch road, county road, loops, spurs, etc.
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